Cordless electrically-powered concrete screed

ABSTRACT

A power unit is configured for use as part of a concrete screed and includes a frame and a powered drive. The frame includes a drive housing. The powered drive is operably supported by the drive housing and is configured to rotate a rotatable concrete forming drum. The powered drive includes an electric motor and a battery operably coupled to the electric motor and configured to power the electric motor. The powered drive includes a drive shaft drivingly connectable relative to the drum, with rotation of the drive shaft causing corresponding rotation of the drum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of prior application Ser. No. 16/560,689, filedSep. 4, 2019, entitled CORDLESS ELECTRICALLY-POWERED CONCRETE SCREED,which claims the benefit of U.S. Provisional Application Ser. No.62/726,849, filed Sep. 4, 2018, entitled BATTERY POWERED CONCRETESCREED, each of which is hereby incorporated in its entirety byreference herein.

The '689 application was filed contemporaneously with U.S.Nonprovisional application Ser. No. 16/560,741 entitled CONCRETE SCREEDPOWER CONTROL LINKAGE, and U.S. Nonprovisional application Ser. No.16/560,749 entitled DRIVE COUPLER FOR DRILL OUTPUT SHAFT, each of whichis also hereby incorporated in its entirety by reference herein.

BACKGROUND 1. Field

The present invention relates generally to concrete equipment used forforming, grading, or screeding concrete. In particular, embodiments ofthe present invention concern a cordless electrical power unit for ascreed.

2. Discussion of Prior Art

Various types of concrete structures, such as slabs, walkways, andwalls, are conventionally graded, formed, and/or finished to present anexposed surface with a desired grade and surface texture. In the usualmanner, forms are erected to define boundaries of the concrete structureand may serve as a guide for grading, forming, and/or finishing theexposed surface.

Powered concrete forming tools have long been available to form, float,or trowel a poured concrete area. Conventional powered forming tools areknown to receive power from different types of power sources, such as aninternal combustion engine, a hydraulic power source, or a cordedelectric power source.

However, prior art concrete forming tools have certain deficiencies.Powered concrete forming tools are used in harsh operating conditions.As such, powered concrete forming tools are well known as being bulkyand heavy, such that the tool is difficult to transport and operate in aprecise manner. For instance, powered screeds generally require morethan one operator to advance the screed and are difficult to manipulate.Known powered screeds include a pair of screed handles that arecooperatively used to advance the screed. The handles are attached toends of a rotatable drum and are shiftable laterally so that operatorscan hold the handles while walking alongside concrete forms. However,lateral shifting of the handles can cause difficulties with screedmanipulation and increases the likelihood of damaging the screed.Conventional powered tools also lack robust operator control features,such that the conventional tools are unduly prone to premature wear anddamage.

This background discussion is intended to provide information related tothe present invention which is not necessarily prior art.

SUMMARY

The following brief summary is provided to indicate the nature of thesubject matter disclosed herein. While certain aspects of the presentinvention are described below, the summary is not intended to limit thescope of the present invention.

Embodiments of the present invention provide a power unit for a concretescreed that does not suffer from the problems and limitations associatedwith prior art devices, including those problems set forth above.

An aspect of the present invention concerns a power unit for a concretescreed including a rotatable concrete forming drum. The power unitbroadly includes a frame and a powered drive. The frame includes a drivehousing. The powered drive is operably supported by the drive housingand is configured to rotate the drum. The powered drive includes anelectric motor and a battery operably coupled to the electric motor andconfigured to power the electric motor. The powered drive includes adrive shaft drivingly connectable relative to the drum, with rotation ofthe drive shaft causing corresponding rotation of the drum.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the embodiments and the accompanyingdrawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Preferred embodiments of the invention are described in detail belowwith reference to the attached drawing figures, wherein:

FIG. 1 is a perspective of a concrete screed constructed in accordancewith a preferred embodiment of the present invention, showing a powerunit, a screed handle, and a rotatable concrete forming drum, with thepower unit being swung into in an advancement position in which thepower unit is angled to one side of the drum for advancement of theconcrete screed along an area of poured concrete;

FIG. 2 is a perspective of the concrete screed similar to FIG. 1, butshowing the power unit swung into an upright parked position in whichthe power unit is angled to the other side of the drum and is standingabove the ground;

FIG. 3 is a fragmentary perspective of the concrete screed shown inFIGS. 1 and 2, showing the power unit in the advancement position, withthe power unit including a frame, a powered drive, a mechanical controlconnection, and a coupler;

FIG. 4 is a fragmentary perspective of the concrete screed shown inFIGS. 1-3, with the frame including a power unit handle and a drivehousing, showing the power unit handle in a central operating position;

FIG. 5 is a fragmentary perspective of the concrete screed similar toFIG. 4, but taken from the opposite side;

FIG. 6 is a fragmentary perspective of the concrete screed shown inFIGS. 1-5, showing the power unit and screed handle exploded away fromthe respective drum ends of the drum;

FIG. 7 is a fragmentary perspective of the drum shown in FIGS. 1-6,showing a tubular drum body and one of the drum ends, with the drum endincluding inboard and outboard flanges, a connection shaft, an elasticsleeve, and fasteners;

FIG. 8 is an enlarged fragmentary elevation of the powered drive andcoupler shown in FIG. 6, showing a coupler body secured to a drive shaftof the powered drive;

FIG. 9 is a fragmentary perspective of the concrete screed shown inFIGS. 1-8, showing part of the drive housing removed to depict parts ofthe powered drive and the mechanical control connection contained by thedrive housing, with the mechanical control connection being configuredto be operated by a lever of the power unit handle and including alinkage and a spring;

FIG. 10 is a fragmentary perspective of the concrete screed similar toFIG. 9, but taken from the opposite side, showing a crank arm, drivelink, connecting link, driven link, and contact arm;

FIG. 11 is a fragmentary top view of the concrete screed shown in FIG.4, showing a drive control element of the powered drive in an offposition and the linkage in a corresponding off condition;

FIG. 12 is a cross section of the concrete screed taken along line 12-12in FIG. 11;

FIG. 13 is a fragmentary perspective of the concrete screed similar toFIG. 11, but showing the lever of the handle swung so that the linkageshifts out of the off condition to shift the drive control elementdistally out of the off position;

FIG. 14 is a fragmentary perspective of the concrete screed similar toFIG. 11, but showing the power unit handle swung to an outboardoperating position;

FIG. 15 is an enlarged fragmentary elevation of the power unit shown inFIGS. 1-6 and 8-14, depicting part of the drive housing broken away todepict the powered drive located within the drive housing, with thepowered drive being mounted to the drive housing in an operatinglocation by support fasteners and a drive adjustment device, and withthe drive adjustment device being adjusted to locate the contact arm ofthe linkage in engagement with the drive control element of the powereddrive;

FIG. 16 is a cross section of the power unit taken along line 16-16 inFIG. 15, with the drive adjustment device including a U-bolt, a plate,threaded nuts, threaded sleeves, and threaded bolts;

FIG. 17 is an enlarged fragmentary elevation of the power unit similarto FIG. 15, but showing the powered drive installed in an initiallocation offset from the operating location, with the drive adjustmentdevice being operable to move the powered drive from the initiallocation to the operating location;

FIG. 18 is an elevation of the power unit shown in FIGS. 1-6 and 8-17,depicting the power unit handle swung to a transport position;

FIG. 19 is a perspective of the power unit as depicted in FIG. 18;

FIG. 20 is a perspective of the power unit similar to FIG. 19, but takenfrom the opposite side;

FIG. 21 is a fragmentary perspective of the power unit shown in FIGS.1-20, with a cover of the drive housing removed and an access dooropened, and with the powered drive detached from the drive housing and abattery removed from the powered drive;

FIG. 22 is a fragmentary perspective of the power unit similar to FIG.21, but taken from the opposite side to depict the interior of the drivehousing;

FIG. 23 is a fragmentary perspective of the power unit similar to FIG.21, but showing the powered drive mounted within the drive housing andlocated to receive the battery;

FIG. 24 is a fragmentary schematic view of the powered drive shown inFIGS. 13-23, depicting the battery, the drive control element, anelectric motor, and a transmission of the powered drive;

FIG. 25 is a fragmentary perspective of a power unit constructed inaccordance with a second preferred embodiment of the present invention,depicting a drive housing, an alternative powered drive, and analternative coupler, with the coupler including a coupler body and afastener;

FIG. 26 is a perspective of the coupler body shown in FIG. 25; and

FIG. 27 is a fragmentary elevation of the power unit shown in FIG. 25,showing the coupler body cross-sectioned.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. While the drawings do notnecessarily provide exact dimensions or tolerances for the illustratedcomponents or structures, the drawings, not including any purelyschematic drawings, are to scale with respect to the relationshipsbetween the components of the structures illustrated therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to FIGS. 1-5, a power unit 30 is provided as part of a poweredconcrete screed 32. The concrete screed 32 is configured to be manuallyadvanced in a forward direction D along poured concrete C (see FIGS. 1and 2). Concrete forms F are constructed to define a space to receivethe poured concrete C. The concrete forms F hold the poured concrete Cwithin the space as the concrete is graded and finished to form aconcrete slab B with a formed surface S.

In the usual manner, the concrete screed 32 is pulled forwardly acrossthe concrete area to screed the poured concrete C and grade the formedsurface S. As the concrete screed 32 is advanced forwardly to grade thesurface S, a rotatable concrete forming drum 34 rotates in rotationdirection R so that excess concrete along the drum 34 is directedforwardly ahead of the drum 34 (see FIGS. 1 and 2).

During operation, it will be understood that the concrete screed 32 canbe used to remove excess concrete material. For example, the concretescreed 32 can remove excess concrete from an area where the pouredconcrete C is above a desired grade level. In the depicted embodiment,the desired grade level is defined by an upper edge of the forms F.Preferably, the drum 34 rests on the upper edge of the forms F duringscreed advancement to grade the formed surface S at the desired gradelevel.

The concrete screed 32 can also be used to transfer concrete from onearea for use in another area. For instance, the concrete screed 32 cantransfer excess concrete to an area where the poured concrete C is belowthe desired grade level.

The formed surface S of the depicted concrete slab B is generally flat(i.e., planar) and level relative to a horizontal plane. It will also beappreciated that the concrete screed 32 can be used to grade the surfaceof a concrete slab so that the surface is flat (i.e., planar) and slopedrelative to the horizontal plane. For instance, one of the concreteforms F could be positioned higher than the other concrete form F.

For certain aspects of the present invention, the concrete screed couldbe configured to form a graded surface that is not flat. For instance,the formed surface could be shaped to include a convex shape and/or aconcave shape. In alternative embodiments, the formed surface may beshaped so that the graded concrete forms at least part of another typeof concrete structure (e.g., a walkway, wall, drainage ditch, orcurbing).

The concrete screed 32 broadly includes the power unit 30, the rotatableconcrete forming drum 34, and a screed handle 36.

Rotatable Concrete Forming Drum

Turning to FIGS. 5-7, the drum 34 is operable to be rotated by the powerunit 30. As will be explained, the drum 34 is rotatable to engageconcrete along the length of the drum 34 and direct at least someconcrete forwardly ahead of the drum 34. The drum 34 preferably includesa drum body 38 and drum ends 40 a,b.

The drum body 38 is operable to engage the poured concrete C to form thegraded surface S. The depicted drum body 38 preferably comprises aunitary cylindrical tube that presents an outer cylindrical surface 42and opposite cylinder ends 44. In the usual manner, the cylindricalsurface 42 comprises a surface of revolution about a drum axis A1 (seeFIG. 7). The drum body 38 also presents a continuous tube bore 46extending between the cylinder ends 44.

The drum body 38 is preferably formed of an aluminum tube materialhaving a substantially constant cross section along the length of thedrum. It will be understood that the use of a tubing permits the drumbody 38 to be readily customized to a desired drum length. In manyapplications, the drum body 38 can be formed by cutting a length ofstock tube to the desired drum length. For some aspects of the presentinvention, the drum body could also be formed by fixing multiple tubepieces together.

Although the drum body 38 is preferably comprised of aluminum, it isalso within the scope of the present invention for the drum body toinclude, additionally or alternatively, another metallic material (e.g.,carbon steel or stainless steel) or a synthetic resin material.

In alternative embodiments, the surface 42 could be formed to present analternative surface of revolution about the drum axis A1. For instance,the drum surface could include a frustoconical surface, formed byrevolving a straight line about the drum axis, where the straight lineextends at an oblique angle to the drum axis. The drum surface couldalso include a surface formed by revolving a plane curve about the drumaxis so that the surface includes a concave and/or convex section.

The drum body 38 is cooperatively supported by the drum ends 40 a,b. Aswill be shown, the drum body 38 is also preferably rotatably driven bythe drum end 40 b. Each drum end 40 a,b preferably includes inboard andoutboard flanges 48 a,b, a connection shaft 50, an elastic sleeve 52,and fasteners 54. Each connection shaft 50 presents a transverse hole 50a and is fixed to a respective outboard flange 48 a,b

The fasteners 54 are slidably received by holes in the outboard flanges48 b and extend through the sleeve 52. The fasteners 54 are alsothreaded into threaded holes of the inboard flanges 48 a to secure thesleeve 52 between the flanges 48 a,b. The fasteners 54 can be threadedinto and out of the inboard flanges 48 a to move the flanges 48 a,btoward and away from each other. For instance, when the flanges 48 a,bare engaged with respective ends of the sleeve 52, the flanges 48 a,bcan be drawn toward each other to compress the sleeve 52 axially. Axialcompression of the sleeve 52 causes the sleeve 52 to expand radially sothat the sleeve diameter increases.

Similarly, when the sleeve 52 is axially compressed and radiallyexpanded, the fasteners 54 can be adjusted to move the flanges 48 a,baway from each other. As the flanges 48 a,b move away from each other,the compressed sleeve 52 is allowed to resiliently expand in the axialdirection. Axial expansion of the sleeve 52 causes the sleeve 52 tocontract radially so that the sleeve diameter decreases.

The illustrated drum 34 can be selectively assembled by engaging thedrum ends 40 a,b within respective cylinder ends 44 of the drum body 38.More specifically, the flanges 48 a,b of each drum end 40 a,b arepositioned so that the sleeve diameter is sized to permit insertion andremoval of the sleeve 52 relative to the cylinder end 44. Preferably,the sleeve diameter is less than the tube bore diameter of the cylinderend 44 when inserting or removing the drum end 40 a,b. For some aspectsof the present invention, it may be feasible to insert and/or remove thedrum end 40 a,b when the sleeve 52 is partly expanded (e.g., where thesleeve diameter is the same or slightly larger than the tube borediameter).

Once located within the cylinder end 44, the fasteners 54 of the drumend 40 a,b are preferably adjusted to frictionally secure the drum end40 a,b within the cylinder end 44. In the depicted embodiment, thefasteners 54 are adjusted to move the flanges 48 a,b toward each otherso that the sleeve 52 is axially compressed and radially expanded intoengagement with the tube bore 46. Further axial compression of thesleeve 52 by the flanges 48 a,b causes the sleeve 52 to become radiallycompressed while remaining in conforming contact with the tube bore 46.

The drum ends 40 a,b can be selectively disengaged from the respectivecylinder ends 44. Preferably, the fasteners 54 are adjusted to move theflanges 48 a,b away from each other so that the sleeve 52 axiallyexpands and radially contracts.

It is also within the ambit of the present invention for one or both ofthe drum ends to be alternatively attached to the drum body. As will beshown, the drum ends are configured to cooperatively position the drumduring operation and transport.

Screed Handle

Turning again to FIGS. 1-5, the screed handle 36 is configured toposition the drum 34 by moving the drum end 40 a. The handle 36 includestelescopic proximal and distal handle sections 56 a,b, a coupler shaft58, bearing housing 60, and a bearing 62 that rotatably supports thecoupler shaft 58 relative to the bearing housing 60.

The housing 60 includes a pair of plates 64 and fasteners 66 (see FIG.6). The plates 64 cooperatively receive the bearing 62 and the couplershaft 58 and are removably secured to each other by the fasteners 64.Preferably, the coupler shaft 58 can spin freely relative to the bearinghousing 60 and the rest of the handle 36.

The proximal handle section 56 a includes a tubular body 68 and atransverse bar 70. The bar 70 is attached to a proximal end of the bodyand includes a pair of grips 72. The distal handle section 56 b presentsa proximal section 74 that is telescopically received within a distalsection 76 of the proximal handle section 56 a. The proximal and distalsections 74,76 can be selectively secured to one another with a pin 78.The pin 78 is removable to permit relative sliding and detachment of thesections 74,76. The bearing housing 60 is attached to a distal end ofthe distal handle section 56 b with clips 80 (see FIG. 6). The clips 80preferably allow the handle sections 56 a,b to swing relative to thebearing housing 60.

The coupler shaft 58 presents a socket 82 and aligned fastener holes 84.The socket 82 slidably receives the connection shaft 50 of the drum end40 a. A pin 86 is inserted through the holes 84 of the coupler shaft 58and the hole 50 a of the connection shaft 50 to removably attach theconnection shaft 50 and coupler shaft 58 to one another (see FIG. 6).

When attached to the drum end 40 a, the handle 36 is used to manuallyshift (e.g., pull) the drum end 40 a (e.g., when advancing the screed 32in the forward direction D). At the same time, the handle 36 permits thedrum 34 to rotate relative to the handle 36. As will be explained, thepower unit 30 rotatably drives the drum 34. Preferably, the handle 36and the power unit 30 are cooperatively used to manually advance thedrum 34 (for instance, when the screed 32 is being advanced/pulled inthe forward direction D).

It is within the scope of the present invention for the screed handlemay be alternatively constructed and/or attached relative to the drumend. For instance, the bearing housing and the distal handle sectioncould be alternatively attached to one another (e.g., to permit relativeswinging movement therebetween).

Furthermore, for certain aspects of the present invention, the concretescreed to be devoid of the handle. For instance, the drum could besupported only by the frame associated with the power unit. In such analternative embodiment, the frame of the power unit could be configuredfor attachment to both drum ends.

Power Unit

Turning to FIGS. 9-11, the power unit 30 is drivingly connected to thedrum 34 and is configured to rotate the drum 34. The power unit 30 alsocooperates with the handle 36 to manually advance the drum 34 in theforward direction D. The power unit 30 broadly includes a frame 88, apowered drive 90, a mechanical control connection 92, and a drivecoupler 94.

The powered drive 90 provides a motive power source to drive the drum34. The powered drive 90 includes a power tool case 96, an electricmotor 98, a drive control element 100, a transmission 102, a drive shaft104, and a rechargeable battery 106 (see FIGS. 6, 15, and 24).

In the depicted embodiment, the powered drive 90 is preferably in theform of a cordless right-angle drill that provides continuous,variable-speed drill operation. However, the powered drive 90 could takeother forms, consistent with at least some aspects of the presentinvention.

The power tool case 96 operably supports the electric motor 98, drivecontrol element 100, transmission 102, drive shaft 104, and battery 106during use. The power tool case 96 includes a head section 96 a and ahandle section 96 b. The power tool case 96 is preferably a moldedhousing and preferably includes a synthetic resin material. It will beunderstood that the power tool case can be alternatively constructedwithin the ambit of the present invention.

The electric motor 98 is configured to power the drum and includes arotatable motor shaft 98 a (see FIG. 24). The motor shaft 98 a ispreferably a rotor shaft of the electric motor 98. The electric motor 98preferably comprises a continuous variable-speed drive motor operable todrive the drive shaft 104 through a range of rotational speed.

The battery 106 comprises a conventional rechargeable battery.Preferably, the battery 106 is a lithium-ion battery, but could includeother types of rechargeable battery configurations (e.g., anickel-cadmium battery). The battery 106 is slidably attachable to thehandle section 96 b in an installed condition. When installed, thebattery 106 is operably coupled to the electric motor 98 to supplyelectrical power to the motor 98 via operation of the drive controlelement 100 (see FIGS. 17 and 24).

The drive shaft 104 extends into and out of the power tool case 96 todefine a shaft end 108 operable to be drivingly attached to the drivecoupler 94 (see FIGS. 6 and 8). In the depicted embodiment, the shaftend 108 presents external threads 110 and an internal threaded bore 112that are generally coaxial with one another and coaxial with a rotationaxis A2 of the drive shaft 104 (see FIGS. 6 and 8).

Preferably, the external threads 110 are opposed to the threads of theinternal threaded bore 112. In particular, the external threads 110 areright-handed and the threads of the internal threaded bore 112 areleft-handed, in the illustrated embodiment. It is also within the ambitof the present invention to reverse the thread orientations, with theexternal threads being left-handed and the threads of the internalthreaded bore being right-handed.

Turning to FIG. 24, the transmission 102 drivingly interconnects theelectric motor 98 and the drive shaft 104 so that the drive shaft 104 ispowered by the electric motor 98 to rotate the drum 34. In particular,the transmission 102 transmits power from the motor shaft 98 a to thedrive shaft 104. Preferably, the transmission 102 enables the motorshaft 98 a and the drive shaft 104 to be arranged at a right angle toone another. It will be appreciated that the transmission may include atransmission ratio configured to increase or decrease the rotationalspeed of the drive shaft relative to the motor shaft.

It is within the ambit of the present invention for the transmission tobe alternatively configured for transmitting power to the drive shaft.For instance, according to some aspects of the present invention, thetransmission may be configured so that the drive shaft does not extendat a right angle to the motor shaft.

Additionally, for some aspects of the present invention, a right-angleconfiguration may alternatively be provided by mounting the electricmotor in the head section 96 a or adjacent thereto, with the handlesection of the case extending transversely relative to the drive shaftof the drive. Also in alternative embodiments, the powered drive couldbe devoid of the transmission, such that the motor shaft (e.g., rotorshaft) provides the drive shaft of the powered drive.

Turning to FIGS. 11, 13, and 15, the drive control element 100 isshiftable to control the electric motor 98 and thereby the rotationalspeed of the drum 34. The drive control element 100 preferably includesa shiftable button.

The depicted drive control element 100 is shiftable into and out of anoff position in which the drive shaft 104 is not rotating (see FIGS. 11and 15). Preferably, the drive control element 100 is spring-biased intothe off position.

Because the powered drive 90 is operable to provide continuous,variable-speed operation, the depicted drive control element 100 ispreferably shiftable through a range of “on” positions in which thedrive shaft 104 rotates (see FIG. 13). In the usual way, as the drivecontrol element 100 is progressively moved further out of the offposition, the rotational speed of the drive shaft 104 proportionallyincreases.

As will be explained, the drive control element 100 and a drivecontroller associated with the frame 88 are variably positionable. Theposition of the drive controller and thereby the position of the drivecontrol element 100 correspond to the rotational speed of the driveshaft 104.

Again, the powered drive 90 is preferably provided by a cordlessright-angle drill. However, elements of the powered drive could beprovided by an alternative cordless power tool. For certain aspects ofthe present invention, the powered drive could also include a cordedpower drive.

For some alternative embodiments associated with the present invention,components of the powered drive could be incorporated as part of thepower unit without being provided as part of an off-the-shelf powertool.

As will be discussed, the powered drive 90 is operably supported by adrive housing associated with the frame 88. The powered drive 90 is alsopreferably operated via a linkage provided as part of the mechanicalcontrol connection 92.

The drive coupler 94 is configured to facilitate removable attachment ofthe power unit 30 to the drum 34 and to impart rotation of the driveshaft 104 to the drum 34. As described below, the drive coupler 94 isconfigured to align the drive shaft 104 and the connection shaft 50 ofthe drum end 40 b on a common rotation axis A2 without permittingoff-axis swinging of the shafts 50,104 relative to one another.

The depicted drive coupler 94 includes a coupler body 114, a screw 116,and a removable pin 118 (see FIGS. 6 and 8). The coupler body 114 ispreferably a rigid and unitary structure and presents opposite connectorportions 120,122 (see FIGS. 6 and 8). The preferred connector portions120,122 present respective sockets 120 a,122 a (see FIG. 8). The couplerbody 114 also presents a bore 124 extending axially between the sockets120 a,122 a so that the sockets 120 a,122 a communicate with one another(see FIG. 8). As will be explained, the connector portion 120 isremovably attached to the drive shaft 104 and the connector portion 122is removably attached to the connection shaft 50 of the drum end 40 b.

In the illustrated embodiment, the connector portion 120 presents thesocket 120 a to receive a corresponding part of the drive shaft 104. Forsome aspects of the present invention, the drive shaft may alternativelyinclude a socket to receive the connector portion of the coupler body.

Preferably, the connector portion 120 includes internal threads 126associated with the socket 120 a to engage the external threads 110 ofthe drive shaft 104 (see FIG. 8). As a result, the connector portion 120and the drive shaft 104 are threadably engaged and coaxial with oneanother. The illustrated connector portion 120 and drive shaft 104 areconsequently attached relative to one another without permittingoff-axis swinging therebetween.

It is contemplated within certain aspects of the present invention forthe connector portion 120 and/or the drive shaft 104 to includealternative complemental features that drivingly engage one another. Forinstance, as will be shown in an alternative embodiment, the connectorportion and drive shaft could include a drive connection formed bycomplemental slot and key features.

The screw 116 preferably comprises a socket head cap screw and isconfigured to further secure the connector portion 120 to the driveshaft 104. Although the depicted screw 116 is preferred, alternativefasteners (e.g., other threaded fasteners, clips, snap rings, etc.) mayused to further secure the connector portion to drive shaft, inaccordance with at least some aspects of the present invention.

The screw 116 is inserted through the bore 124 of the coupler body 114and is threaded into engagement with the internal threaded bore 112 ofthe drive shaft 104. Preferably, the internal threads 126 of theconnector portion 120 are opposed to the threads of the screw 116. As aresult, the coupler body 114 rotates in one direction onto the driveshaft 104, while the screw 116 rotates in the opposite direction intoengagement with the threaded bore 112 of the drive shaft 104. In thedepicted embodiment, the internal threads 126 are right-handed and thethreads of the screw 116 are left-handed. It is also within the ambit ofthe present invention for the thread orientations to be reversed, withthe internal threads of the connector portion being left-handed and thethreads of the screw being right-handed.

The connector portion 122 of the coupler body 114 presents the socket122 a and aligned fastener holes 128. The illustrated socket 122 aincludes a smooth bore and is configured to receive part of theconnection shaft 50 of the drum end 40 b. The socket 122 a is coaxialwith the rotation axis A2, and the fastener bore 128 extendstransversely to the rotation axis A2.

The pin 118 of the drive coupler 94 is associated with the connectorportion 122 to secure the connector portion 122 to the connection shaft50 of the drum end 40 b. Preferably, the pin 118 is removably insertedthrough the fastener holes 128 and hole 50 a to drivingly engage thecoupler body 114 and the connection shaft 50. The illustrated connectorportion 122 and the connection shaft 50 are consequently attachedrelative to one another without permitting off-axis swingingtherebetween.

It is also consistent with at least some aspects of the presentinvention for the coupler body and the connection shaft to bealternatively connected relative to one another. For instance, thecoupler body and the connection shaft could be joined by a connectionstructure other than a pinned joint (e.g., a threaded joint and/or ajoint with a key-and-slot configuration). Yet further, the connectorportion 122 and connection shaft 50 may alternatively be constructed toprevent relative rotational movement therebetween. For example, theconnector portion and connection shaft may have complemental,non-circular, shapes (e.g., splined, polygonal, etc.) for rotatablyfixing the components to one another.

The illustrated drive coupler 94 is configured to align the drive shaft104 and connection shaft 50 of the drum end 40 b on a common rotationaxis A2 without permitting off-axis swinging of the shafts 50,104relative to one another. (Those of ordinary skill in the art willappreciate off-axis swinging means positioning of the shaft at an angle(more than mere resilient deflection) relative to the rotation axis A1.)The illustrated drive coupler 94 is consequently configured to restrictswinging of a drive housing of the frame 88 relative to the drum 34.

Turning to FIGS. 3-5 and 9-23, the frame 88 preferably includes a drivehousing 130 and a power unit handle 132 to be grasped by a user tofacilitate manual advancement of the concrete screed 32 in the forwarddirection D.

In the depicted embodiment, the power unit handle 132 of the frame 88and the screed handle 36 can be manually manipulated by respective usersso that the handles 36,132 can cooperatively advance the concrete screed32.

As will be explained, the handle 132 and drive housing 130 are pivotallyattached relative to each other so that the handle 132 is swingablerelative to the drive housing 130 about a frame pivot axis P (see FIG.18) that is transverse to the forward direction D.

Turning to FIGS. 18-23, the drive housing 130 preferably extends along ahousing axis H1 to present proximal and distal housing ends 134 a,b (seeFIGS. 3 and 18-20). The illustrated drive housing 130 includes a shell136, a pivot bracket 138, an access door 140, and a housing handle 142(see FIGS. 3-5 and 18-20).

The shell 136 is configured to enclose substantial parts of themechanical control connection 92 and the powered drive 90. The depictedshell 136 includes a channel 144 and a cover 146 that cooperativelydefine a drive chamber 148 to at least partly receive the powered drive90 (see FIGS. 15 and 16).

The channel 144 includes a base wall 144 a and side walls 144 b thatextend along the housing axis H1. The side walls 144 b includeprojections 150 configured to support the powered drive 90, as will beexplained below (see FIGS. 18-21).

The side walls 144 b of the channel 144 also include tabs 152 thatcooperatively support the housing handle 142 adjacent the proximalhousing end 134 a (see FIGS. 2 and 18-22). The handle 142 includes atube section 142 a and a fastener 142 b that secures the tube section142 a between the tabs 152 (see FIG. 22). The handle 142 preferablyprovides a location for grasping the drive housing 130. By providing agrip associated with the frame 88, the handle 142 can be used tocarrying the power unit 30 (e.g., when the handle 132 is folded into thetransport position). Additionally, the handle 142 is suitable forgrasping and holding the drive housing 130 in place as the handle 132 isswung between the transport and operating positions.

The channel 144 further presents an access opening 154 that is presentedby the base wall 144 a and the side walls 144 b (see FIGS. 18, 21, and23). The access opening 154 communicates with the chamber 148 andpermits insertion and removal of the battery 106 relative to the chamber148.

The access door 140 has a unitary construction and is pivotally mountedto the channel 144 by a fastener 156. The door 140 is preferablyoperable to swing into and out of a closed condition in which the door140 substantially covers the access opening 154 and restricts access tothe battery 106 (see FIG. 18). The door 140 can also be selectivelyopened to permit battery insertion and removal (see FIGS. 21 and 23).

The cover 146 is removably attached to respective margins of the sidewalls 144 b by fasteners 158 so that the cover 146 spans the areabetween the side walls 144 b (see FIGS. 16, 18, and 19). The cover 146and channel 144 cooperatively define a distal opening 160 that isconfigured to receive a respective part of the powered drive 90 (seeFIG. 19).

The pivot bracket 138 is configured to be attached to the power unithandle 132. The bracket 138 is fixed to the channel 144 and includesopposed bracket plates 162 (see FIGS. 18 and 19). The plates 162 eachpresent a hole 162 a to receive a pivot pin 164 (see FIGS. 18 and 19)and present holes 162 b,c to receive a locating pin 166 (see FIGS.18-23).

In alternative embodiments, the drive housing may be configured withouta shell that encloses substantial parts of the linkage and the powereddrive. For some aspects of the present invention, the drive housing maybe constructed so that additional features of the powered drive areexposed.

The powered drive 90 is operably and adjustably supported by the drivehousing 130 within the drive chamber 148. The power unit 30 includessupport fasteners 168 and a drive adjustment device 170 to adjustablysupport the powered drive 90 relative to the drive housing 130 (seeFIGS. 15-17).

Support fasteners 168 swingably attach the powered drive 90 relative tothe drive housing 130 at a support joint 172. The powered drive 90 issupported at the joint 172 to swing about a mounting axis M extendingtransversely to the housing axis H1 (see FIGS. 15-17). The support joint172 is provided by swingably attaching the projections 150 of the drivehousing 130 to the power tool case 96 with support fasteners 168. Inparticular, the support fasteners 168 are located to extend throughrespective holes presented by the projections 150. The support fasteners168 are configured to be threaded into sockets (not shown) of the powertool case 96.

The drive adjustment device 170 shiftably attaches the power tool case96 to the drive housing 130 at a location spaced from the support joint172. The drive adjustment device 170 is configured to swingably positionthe powered drive 90 relative to the drive housing 130.

The drive adjustment device 170 preferably includes a U-bolt 174, aplate 176, threaded nuts 178, threaded sleeves 180, and threaded bolts182 (see FIGS. 15-17). The U-bolt 174 and plate 176 are fastened to oneanother by nuts 178 and secured around the handle section 96 b of thepower tool case 96.

The sleeves 180 and bolts 182 are configured to rotate relative to theU-bolt 174 for shifting the handle section 96 b about the mounting axisM. As the handle section 96 b is moved, the powered drive 90correspondingly swings about the mounting axis M. As will be explained,the drive adjustment device 170 is operable to swing the powered drive90 so that the drive control element 100 can be selectively positionedin relation to the mechanical control connection 92.

For at least some aspects of the present invention, the power unit couldinclude an alternative adjustment mechanism to adjustably position thepowered drive relative to the drive housing.

Also, for certain aspects of the present invention, the power unit maynot include an adjustment mechanism. For example, another component ofthe power unit (e.g., the linkage) could be adjustable to providesuitable operation of the power unit.

With the powered drive 90 supported in the drive housing 130, thebattery 106 is selectively inserted and removed relative to the drivechamber 148 by moving the battery 106 through the access opening 154(see FIGS. 21 and 23).

Once inserted at least partly within the drive chamber 148 via theaccess opening 154, the battery 106 is selectively attached to thehandle section 96 b (see FIGS. 17 and 23). Similarly, the battery 106 isslidably detachable from the handle section 96 b and removable from thedrive chamber 148 via the access opening 154 (see FIGS. 17 and 23).

The power unit 30 also preferably includes a support stand 184adjustably attached relative to the drive housing 130 and extendingtransversely relative to the housing axis H1 (see FIGS. 1 and 2).

The support stand 184 is elongated and includes a ground-engaging end184 a and a threaded attachment end 184 b (see FIG. 20). The supportfasteners 168 each preferably include a threaded socket 168 a (see FIG.6) for connection to the attachment end 184 b. The support stand 184 isconfigured to be removably attached to either side of the powered drive90.

When attached to the powered drive 90, the support stand 184 isconfigured to engage the ground and in part support the drive housing130 in an upright orientation (see FIG. 2). When parked in the uprightorientation, the power unit 30 is angled to one side of the drum 34 andthe support stand 184 extends downwardly from the powered drive 90 toengage the ground or another surface (see FIG. 2).

In alternative embodiments, the support stand can be alternativelyconfigured and/or associated with the drive housing without departingfrom the scope of the present invention. For instance, the support standand drive housing could be directly attached to one another.

When the concrete screed 32 is assembled, the power unit 30 can beselectively parked in the upright orientation. In particular, when thedrum 34 is supported on the form F (or another support surface) and thesupport stand 184 is also supported on a surface (such as the ground),the support stand 184 and the drum 34 generally cooperate to support thepower unit 30 in the parked upright orientation.

For advancement of the concrete screed, the power unit 30 can be swungover to a position where the power unit 30 is angled to the other sideof the drum 34 (see FIG. 1). In this position, the support stand 184extends upwardly from the support fastener 168 and is spaced above theground (see FIG. 1).

It will also be appreciated that the support stand 184 can be detachedfrom the powered drive 130 and stored on the power unit handle 132 inpreparation for screed advancement (see FIG. 20). In this way, the powerunit 30 can be angled to either side of the drum 34 for purposes ofadvancing the screed 32.

Turning to FIGS. 18-23, the power unit handle 132 is configured tofacilitate manual advancement of the concrete screed 32 in the forwarddirection D. The handle 132 includes a handle body 186, a transverse bar188, a pair of opposed plates 190, a stand storage bracket 192, and ashiftable user-operated drive controller 194.

The handle body 186 extends along a handle axis H2 and presents proximaland distal ends 186 a,b (see FIGS. 11 and 18). The body 186 presents anopen channel 196 that extends axially between the proximal and distalends 186 a,b (see FIGS. 12 and 20). As will be explained, the body 186is pivotally attached to the pivot bracket 138 of the drive housing 130adjacent the distal end 186 b. The bar 188 is attached to the proximalend 186 a of the body 186 and includes a pair of grips 198 a,b (seeFIGS. 11 and 18).

The drive controller 194 preferably comprises a lever pivotal relativeto the grips 198 a,b. The drive controller 194 is integrally formed witha crank arm of the mechanical control connection 92. The drivecontroller 194 is pivotally attached to the plates 190 with a fastener200 at a first location adjacent the grip 198 a (see FIGS. 18 and 20).Some aspects of the present invention contemplate the use of analternative controller (e.g., a push button, a switch not clasped withinthe user's palm, etc.).

The drive controller 194 is also configured to be attached to the platesat a second location adjacent the grip 198 b on the opposite side of thehandle body 186. Thus, the drive controller 194 is operable to beconfigured for either right-handed or left-handed operation.

The power unit handle 132 and drive housing 130 are pivotally attachedrelative to each other, In particular, the handle 132 is swingablerelative to the drive housing 130 about the frame pivot axis P, which isgenerally transverse to the forward direction D. Preferably, the body186 of the handle 132 is pivotally attached to the bracket 138 of thedrive housing by the pivot pin 164. The body 186 is also selectivelyattached to the bracket 138 by the locating pin 166.

Turning to FIGS. 18-20, the depicted handle 132 is operable to swingbetween any of several operating positions and a transport position. Inthe transport position, the handle 132 extends from the frame pivot axisP to at least partly extend alongside the drive housing 130, such thatthe frame 88 is folded. The locating pin 166 is selectively positionedto extend through the bracket 138 and the handle 132 to restrictmovement out of the transport position.

Also in the transport position, the power unit 30 defines a transportcenter of gravity CG (see FIG. 18). The handle 132 preferably extendsaxially on opposite sides of the transport center of gravity CG in thetransport position when the housing axis H1 is oriented laterally tofacilitate manual carrying of the power unit. In the transport position,the handle 132 preferably extends so that the handle 132 and the drivehousing 130 are generally coextensive with one another. For some aspectsof the present invention, the frame could have an alternative transportposition (e.g., where the handle is alternatively oriented relative tothe drive housing).

Turning to FIGS. 11-14 and 21-23, in each of the operating positions,the handle 132 extends outwardly relative to the drive housing 130. Theoperating positions preferably include a series of discrete positions inwhich the handle 132 can be fixed (such that swinging of the handle 132relative to the drive housing 130 is restricted). The discrete positionsinclude an inboard position, a central position, and an outboardposition.

In any one of the discrete positions, the locating pin 166 isselectively positioned to extend through corresponding bracket holes 162b (see FIG. 18) in the bracket 138 and a corresponding hole in thehandle 132. The bracket holes 162 b are associated with the inboard,central, and outboard positions, respectively. The locating pin 166 issecured in any one of the operating positions to restrict movement outof that position. In one example, the locating pin 166 can be used tosecure the handle 132 in the central position (see FIG. 11) andsubsequently used to secure the handle 132 in the outboard position (seeFIG. 14).

The frame 88 is also preferably configured to provide operatingpositions, other than the inboard, central, and outboard positions, forwhich the handle 132 and drive housing 130 are not joined by thelocating pin 166. For instance, the handle 132 could be located betweenthe outboard position and the central position. The depicted handle 132also preferably provides operating positions inboard of the inboardposition. Similarly, the handle 132 preferably provides operatingpositions outboard of the outboard position (up to the point at whichthe handle 132 contacts a corner of the drive housing 130).

When operating the power unit 30 without securing the locating pin 166to the handle 132 and drive housing 130, it will also be understood thatthe handle 132 is preferably freely swingable among a range of operatingpositions.

For some aspects of the present invention, the frame could have one ormore alternative operating positions (e.g., where the handle isalternatively oriented relative to the drive housing).

In use, the frame 88 of the power unit 30 and the screed handle 36 arecooperatively used to manually advance the drum 34 in the forwarddirection D. When the power unit 30 is attached to the drum end 40 b ofthe drum 34, the power unit handle 132 can be located in one of theoperating positions and used to manually shift (e.g., pull) the drum end40 b (e.g., in the forward direction D). At the same time, the frame 88permits the drum 34 to rotate relative to the power unit handle 132.

The power unit 30 can be selectively prepared for transport by beingdetached from the drum end 40 b and by swinging the power unit handle132 to the transport position. In alternative embodiments, the powerunit handle could be variously configured without departing from thescope of the present invention.

According to certain aspects of the present invention, the power unithandle 132 and the drive housing 130 may alternatively be attachedrelative to one another. For example, in alternative embodiments, thepower unit handle could be shiftably attached relative to the drivehousing with an alternative pivot connection and/or a slidingconnection. Also, for some aspects of the present invention, the powerunit handle could be fixed relative to the drive housing.

Although the screed 32 preferably involves the use of both the powerunit 30 and the screed handle 36, for some aspects of the presentinvention, the screed may alternatively utilize an alternative handleconfiguration.

For instance, the screed may alternatively be configured to use only asingle handle (e.g., a handle like the power unit handle 132) tomanually shift (e.g., pull) the screed. In such an alternativeembodiment, the frame of the power unit may be configured for attachmentrelative to both drum ends. It will be appreciated that such analternative construction may be more suitable for instances when thedrum presents a relatively short drum length.

Turning to FIGS. 9-14, the mechanical control connection 92 isconfigured to facilitate selective operation of the powered drive 90when the power unit handle 132 is in one of the operating positions. Themechanical control condition 92 is preferably shiftable into and out ofan off condition associated with the off position of the drive controlelement 100. As will also be explained, the mechanical controlconnection 92 preferably restricts operation of the powered drive 90when the handle 132 is in the transport position.

In the illustrated embodiment, the mechanical control connection 92extends between the drive controller 194 and the drive control element100 so that shifting of the drive controller 194 corresponds withshifting of the drive control element 100. The mechanical controlconnection 92 preferably includes a linkage 202 and a spring 204.

The linkage 202 is operably interposed between the drive controller 194and the drive control element 100. As will be explained, the linkage 202is configured so that the drive controller 194 is shiftable to operatethe powered drive 90 when the handle 132 is in an operating position.Also, the drive controller 194 is restricted from operating the powereddrive 90 when the handle 132 is in the transport position. When locatedin an operating position, the linkage 202 is shiftable into and out ofthe off condition.

The linkage 202 in the illustrated embodiment includes a crank arm 206,a slidable drive link 208, a rotatable driven link 210, a connectinglink 212, and a contact arm 214 (see FIG. 9).

In the preferred embodiment, the crank arm 206 is integrally formed withthe drive controller 194. The crank arm 206 and drive controller 194 arepivotally attached to the plates 190 with a fastener at a first locationassociated with the grip 198 a (see FIG. 20). Again, the crank arm 206and drive controller 194 are also configured to be attached to theplates 190 at a second location associated with the grip 198 b.

The drive link 208 is unitary and extends axially to define proximal anddistal link ends 208 a,b associated with the proximal and distal ends186 a,b. The drive link 208 includes an elongated link body 216 a and atab 216 b associated with the distal link end 208 b (see FIGS. 12 and20).

The drive link 208 is at least partly located within the open channel196 and is slidably attached to the handle 132 with a fastener 218 (seeFIGS. 12 and 20). Preferably, the drive link 208 is slidable relative tothe handle 132 along a link axis L parallel to the handle axis H2 (seeFIG. 11). For at least certain aspects of the present invention, thedrive link 208 could be alternatively shiftably supported relative tothe handle 132.

The proximal link end 208 a of the drive link 208 is operable to beslidably engaged by the crank arm 206. As will be explained, the drivelink 208 is spring-biased toward a proximal position associated with theoff condition. As the user engages the drive controller 194 to rotatethe crank arm 206 distally, the crank arm 206 shifts the drive link 208distally along the handle axis H2.

The connecting link 212 is unitary and includes a pair of endmost yokes220 that present respective slots 222 (see FIGS. 12 and 20). One of theyokes 220 receives the tab 216 b in the corresponding slot 222 and ispivotally attached to the tab 216 b with a pin 224 (see FIG. 20). Theother yoke 220 receives the driven link 210 and is pivotally attached tothe driven link 210 with another pin 224 (see FIG. 20).

The driven link 210 is also unitary and includes a pair of link arms226,228. The link arms 226,228 extend radially from a link base 230 topresent spaced-apart link ends 226 a,228 a (see FIG. 11). The contactarm 214 is attached to the link arm 228 adjacent the link end 228 a andextends transversely from the link arm 228 (see FIGS. 15 and 16).

In the depicted embodiment, the link base 230 is pivotally attached tothe channel 144 so that the driven link 210 is located partly within thedrive chamber 148 and pivots at a link joint 232 (see FIG. 11). The linkarm 226 extends through an elongated slot 234 (see FIG. 20) presented bythe drive housing 130 so that the link end 226 a is located outside ofthe drive housing 130. The link end 226 a is pivotally attached to oneyoke 220 of the connecting link 212 to form a linkage pivot joint 236that permits relative pivoting about a linkage pivot axis T (see FIG.23).

The driven link 210 is rotatable into and out a stop position associatedwith the off condition of the linkage 202. In the stop position, aportion of the drive housing 130 provides a stop 238 (see FIG. 20) toengage the driven link 210 and restrict proximal shifting of the drivenlink 210.

As the user engages the drive controller 194 to rotate the crank arm 206distally, the crank arm 206 shifts the drive link 208 and the connectinglink 212 distally along the handle axis H2. The connecting link 212correspondingly swings the driven link 210 about the link axis L so thatthe link end 228 a and the drive control element 100 move distally.

The configuration of the depicted linkage 202 allows the power unithandle 132 to be folded relative to the drive housing 130 when thelinkage 202 is in the off condition. As noted, the linkage pivot axis Tallows the driven link 210 to swing relative to the connecting link 212and the drive link 208. Preferably, the linkage pivot axis T is arrangedto be generally parallel to the frame pivot axis P (see FIG. 23).Furthermore, the frame pivot axis P and the linkage pivot axis T arepreferably adjacent one another, with any relative axial offset beingrelatively small, particularly when the linkage 202 is in the offcondition (see FIG. 23). It will be appreciated that the connecting link212, including the slots 22, is configured to accommodate the relativeoffset of the frame pivot axis P and linkage pivot axis T. With thisarrangement of the linkage pivot axis T, the linkage 202 permitsswinging of the handle 132 in the off condition. For some aspects of thepresent invention the frame pivot axis P and linkage pivot axis T couldbe alternatively positioned relative to each other (e.g., the axes P,Tcould be coaxial).

In the depicted embodiment, it will be appreciated that the linksprovided by the linkage all comprise rigid structural elements. That is,each of the crank arm 206, slidable drive link 208, rotatable drivenlink 210, connecting link 212, and contact arm 214 is a rigid structure.That is, the illustrated linkage is preferably devoid of a continuouslyflexible element (such as a cable, string, rope, etc.) capable of beingtransmitting a tension force. However, it is contemplated within certainaspects of the present invention for the linkage to include acontinuously flexible element.

The linkage 202 could be variously alternatively configured to providedesired linkage operation and handle-folding capability, in accordancewith at least some aspects of the present invention. It is alsocontemplated, within particular aspects of the present invention, thatthe linkage could restrict folding of the handle (e.g., for frameembodiments where the handle and drive housing a rigidly attached to oneanother).

The linkage 202 preferably enables the drive controller 194 and thedrive control element 100 to be variably positionable, with the positionof the drive controller 194 corresponding to a position of the drivecontrol element 100.

The linkage 202 is configured to be shifted into and out of an offcondition, which is associated with the drive control element 100 in theoff position, when the power unit handle 132 is in one of the operatingpositions (see FIG. 11). For instance, when the handle 132 is in anoperating position, the crank arm 206 and links 208,210,212 arecooperatively shiftable to move the drive control element 100 out of theoff position. However, in the preferred embodiment, the linkage 202 isrestricted from moving out of off position when the handle 132 is in thetransport position.

As explained above, the depicted drive control element 100 is preferablyshiftable through a range of “on” positions in which the drive shaft 104rotates so that the powered drive 90 provides continuous, variable-speedoperation. In particular, as the drive control element 100 isprogressively moved further out of the off position, the rotationalspeed of the drive shaft 104 proportionally increases.

As the user engages the drive controller 194 to rotate the crank arm 206distally, the driven link 210 swings about the link axis L so that thelink end 228 a engages the drive control element 100 and moves the drivecontrol element 100 distally away from the off position.

Preferably, as the user progressively moves the crank arm 206 distally,the linkage 202 progressively moves the drive control element 100distally so that the rotational speed of the drive shaft progressivelyincreases.

Although the linkage 202 is freely shiftable in the operating positions,components of the linkage 202 are preferably restricted from shiftingwhen the handle 132 is in the transport position.

The handle 132 is generally shiftable into the transport position whenthe linkage 202 is located in the off condition. With the handle 132folded into the transport position, the driven link 210 preferablyengages the stop 238 of the drive housing 130. The driven link 210 andthe stop 238 engage one another to restrict the links 208,210,212 fromshifting distally out of the off position. Consequently, the driven link210 engages the stop 238 to restrict linkage shifting associated withmovement of the drive control element 100 out of the off position.

It is within the scope of certain aspects of the present invention forthe power unit to be provided with an alternative stop to restrictlinkage movement. For instance, another part of the frame or anotherrelatively stationary structure could be configured to engage thelinkage (e.g., one or more links other than the driven link) to preventshifting of the drive controller (i.e., the lever) out of the offposition when the frame is folded for transport.

The mechanical control connection 92 preferably includes the spring 204to urge the linkage 202 toward the off condition. The illustrated spring204 comprises a coil spring with opposite spring ends 204 a attached tothe channel 144 and the link arm 226, respectively.

As the user moves the crank arm 206 distally to shift the linkage 202out of the off condition, the spring 204 exerts a progressivelyincreasing biasing force against the driven link 210 along a proximaldirection. Consequently, the spring 204 urges the driven link 210 andthe rest of the linkage 202 toward the off condition (and thereby thelever to the off position).

For at least some aspects of the present invention, the spring 204 couldbe alternatively constructed and/or positioned to apply a biasing forceto the linkage 202. For instance, it will be appreciated that a torsionspring could be associated with the link base to urge the driven linktoward the off condition. Similarly, a spring could be configured toapply a biasing force to another part of the linkage (e.g., the lever)to urge the link to the off position.

In operation, the power unit 30 is drivingly attached to the drum 34 bythe drive coupler 94. In particular, the connector portion 120 of thedrive coupler 94 is removably attached to the drive shaft 104, and theconnector portion 122 of the drive coupler 94 is removably attached tothe connection shaft 50 of the drum end 40 b. The drive coupler 94 isoperable to restrict swinging of the power unit 30 relative to the drum34. Similarly, the power unit 30 can be selectively uncoupled from thedrum 34 by detaching the drive coupler 94 from the connection shaft 50and/or the drive shaft 104.

When the power unit 30 is attached to the drum end 40 b of the drum 34,the power unit handle 132 can be located in one of the disclosedoperating positions and used to manually shift the drum end 40 b (e.g.,in the forward direction D). At the same time, the frame 88 permits thedrum 34 to rotate (with the drive shaft 104) relative to the power unithandle 132. When detached from the drum 34 and not in use, the frame 88of the power unit 30 can be selectively folded from an operatingposition to a transport position.

The mechanical control connection 92 is configured to facilitateselective operation of the powered drive 90 when the power unit handle132 is in one of the operating positions. The mechanical controlcondition 92 is preferably shiftable into and out of an off conditionassociated with the off position of the drive control element 100.

As the user shifts the drive controller 194 to swing the crank arm 206distally, the crank arm 206 shifts the drive link 208 and the connectinglink 212 distally along the handle axis H2. The connecting link 212correspondingly swings the driven link 210 about the link axis L so thatthe link end 228 a and the drive control element 100 move distally. Themechanical control connection 92 preferably restricts operation of thepowered drive 90 when the handle 132 is in the transport position.

The power unit handle 132 and the screed handle 36 can be manuallymanipulated by respective users so that the handles 36,132 cancooperatively advance the concrete screed 32 along the poured concreteC. As the concrete screed 32 is advanced forwardly to grade the surfaceS, the drum 34 rotates in rotation direction R so that excess concretealong the drum 34 is directed forwardly ahead of the drum 34 (see FIGS.1 and 2).

Turning to FIGS. 25-27, an alternative power unit 300 is constructed inaccordance with a second preferred embodiment of the present invention.For the sake of brevity, the following description will focus primarilyon the differences of the power unit 300 when compared to the previousembodiment.

The power unit 300 preferably includes, among other things, a frame 302,an alternative powered drive 304, and an alternative coupler 306.

The powered drive 304 includes a power tool case 308 and an alternativedrive shaft 310. The drive shaft 310 extends into and out of the powertool case 96 and includes a rotating base 312 and a shaft end 314. Thebase 312 includes a pair of keys 316 on opposite sides of the shaft end314. The shaft end 314 presents a cylindrical outer surface 318 and aninternal threaded bore 320 that are generally coaxial with one anotherand coaxial with a rotation axis A2 of the drive shaft 310.

The drive coupler 306 is configured to facilitate removable attachmentof the power unit 300 to the drum. The drive coupler 306 is configuredto align the drive shaft 310 and the connection shaft of the drum on acommon rotation axis A2 without permitting off-axis swinging of thedrive shaft 310 and the connection shaft relative to one another.

The drive coupler 306 includes a coupler body 322 and a screw 324. Thecoupler body 322 is preferably a rigid and unitary structure andpresents opposite connector portions 326,328. The connector portions326,328 present respective sockets 326 a,328 a. The coupler body 114also presents a bore 330 extending axially between the sockets 326 a,328a so that the sockets communicate with one another.

Preferably, the socket 326 a has a smooth inner bore 332 to slidablyreceive the shaft end 314 of the drive shaft 310. The connector portionalso presents a drive slot 334 that removably receives the keys 316associated with the drive shaft 310. The keys 316 are drivingly engagedwith the slot 334 to cooperative provide a drive connection between theconnector portion 326 and the drive shaft 310.

The screw 324 is configured to further secure the connector portion 326to the drive shaft 310. The screw 324 is inserted through the bore 332of the coupler body 322 and is threaded into engagement with theinternal threaded bore 320 of the drive shaft 310.

Although the above description presents features of preferredembodiments of the present invention, other preferred embodiments mayalso be created in keeping with the principles of the invention. Suchother preferred embodiments may, for instance, be provided with featuresdrawn from one or more of the embodiments described above. Yet further,such other preferred embodiments may include features from multipleembodiments described above, particularly where such features arecompatible for use together despite having been presented independentlyas part of separate embodiments in the above description.

The preferred forms of the invention described above are to be used asillustration only, and should not be utilized in a limiting sense ininterpreting the scope of the present invention. Obvious modificationsto the exemplary embodiments, as hereinabove set forth, could be readilymade by those skilled in the art without departing from the spirit ofthe present invention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

1. A power unit for a concrete screed including a rotatable concreteforming drum, said power unit comprising: a frame including a drivehousing; and a powered drive being operably supported by the drivehousing and configured to rotate the drum, said powered drive includingan electric motor and a battery operably coupled to the electric motorand configured to power the electric motor, said powered drive includinga drive shaft drivingly connectable relative to the drum, with rotationof the drive shaft causing corresponding rotation of the drum.